Conventionally, separate type air conditioning apparatuses each including an indoor unit and an outdoor unit have been widely used. In the outdoor unit, electric elements such as an air blower and a compressor are arranged in a casing, and an electric component unit in which electric components such as a control board configured to control the electric elements are accommodated is arranged.
In operation of the air conditioning apparatus, the electric component(s) accommodated in the electric component unit generates heat. Such heat generation may increase the temperature of atmosphere inside the electric component unit, resulting in, e.g., damage of the electric component(s). Thus, as in the Patent Document 1, the electric component(s) is cooled in such a manner that an opening or a slit is formed at a side surface of the electric component unit placed inside the casing to ensure an air passage inside the electric component unit.
In Patent Document 1, since air is discharged to the outside of the casing by the air blower, the pressure of air inside the casing is pressure (i.e., negative pressure) lower than atmospheric pressure. Moreover, the electric component unit is arranged inside the casing in which a negative pressure space is formed. In the electric component unit, an airflow is formed by using a pressure difference between air in proximity to the air blower and air distant from the air blower.